Sender Reputation

A score calculated by ISPs based on sending behavior, affecting inbox placement.

1 min readLast updated Apr 2026
Reviewed by Golden Digital·Operator-reviewed ecommerce reference

A score calculated by ISPs based on sending behavior, affecting inbox placement.

Why It Matters

Your sender reputation is like a credit score for email—it determines whether ISPs let your emails through to the inbox or filter them to spam. Built over time through good sending practices, reputation is hard to earn and easy to damage. A poor reputation can take months to rebuild.

Practical Example

Scenario

A wellness brand checks Google Postmaster Tools and sees their domain reputation dropped from 'High' to 'Medium' after a promotional blast to an old segment.

Calculation

Spam complaints spiked to 0.4% on that campaign vs their usual 0.05%

Result

They immediately stop sending to unengaged segments, clean their list, and focus on highly engaged subscribers. After 6 weeks of clean sending, reputation recovers to 'High'.

Pro Tips

  • 1Monitor reputation with Google Postmaster Tools, Microsoft SNDS, and your ESP's deliverability dashboard
  • 2Maintain consistent sending volume—sudden spikes trigger ISP suspicion
  • 3Keep spam complaints under 0.1% and bounces under 2%
  • 4Warm up new IPs/domains gradually before high-volume sending

Common Mistakes to Avoid

Ignoring reputation until deliverability problems become severe
Sending to purchased or rented lists, which generates complaints and bounces
Dramatic volume increases without proper warmup

Frequently asked questions

Google Postmaster Tools (for Gmail), Microsoft SNDS (for Outlook/Hotmail), and third-party tools like Sender Score. Your ESP may also provide reputation metrics in their dashboard.

4-8 weeks of consistent good sending practices. Reduce volume, send only to engaged subscribers, ensure authentication is correct, and gradually rebuild as metrics improve.

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